(1) Field of the Invention
The present invention relates to a fuel spraying method in a liquid fuel combustion burner used for a heating apparatus as a heat source of a boiler, a heating furnace and the like, and a liquid fuel combustion burner. More particularly, the present invention relates to a fuel spraying method in a liquid fuel combustion burner having a structure in which a liquid fuel is sprayed together with a fluid flow of air, steam or a mist of water drops (hereinafter referred to as "atomization-promoting fluid") mixed into the fuel for promoting the atomization of the liquid fuel, and a liquid fuel combustion burner.
(2) Description of the Related Art
A liquid fuel combustion burner having a structure in which a liquid fuel is mixed with an atomization-promoting fluid such as steam or air and the mixed fluid is sprayed from a plurality of injection holes (see Japanese Unexamined Utility Model Publication No. 57-145116) is known.
According to the fuel spraying method adopted for this liquid fuel combustion burner, the liquid fuel to be mixed with the atomization-promoting fluid is atomized and diffused by the expansion energy generated when an atomization-promoting fluid such as steam or air is injected to a low-pressure side from a high-pressure side.
In regards to the above-mentioned spraying method, there are known an internal mixing method in which the injection quantity is controlled while maintaining a certain difference between the pressure of the atomization-promoting fluid and the pressure of the liquid fuel, and an intermediate mixing method in which the pressure of the liquid fuel is changed while maintaining the pressure of the atomization-promoting fluid at a certain level, whereby the injection quantity is controlled.
In these fuel spraying methods, by attaining a slow combustion effect by lowering the flame temperature and reducing the oxygen concentration, control of generation of NO.sub.x is expected while allowing certain generation of soot.
In other words, in the conventional combustion method or fuel spraying method, it is difficult to simultaneously control generation of NO.sub.x and generation of soot.
In the case where fuel injection holes formed in a burner are equidistantly arranged or are distributed in a divided state resembling the equidistant arrangement as disclosed in Japanese Unexamined Utility Model Publication No. 57-145116, generation of soot can be controlled but since the heat dissipation is degraded, control of generation of NO.sub.x is difficult, and it is therefore impossible to simultaneously control generation of NO.sub.x and generation of soot.